HJ 591-2010Water quality. Determination of pentachlorophenol by gas chromatography (English PDF)

4.2 Column

Packed column. made of hard glass or stainless steel, 1.5 to 2.5 m long, 3 to 4 mm in inner diameter, 1.5% phenyl-containing poly-coated Chromsorb W (80-100 mesh) of methyl siloxane (OV-17) and 2% polyfluoroalkylsiloxane (QF-1). Packed column preparation See Appendix A for the method.

Capillary column. The stationary phase was 5% phenyl-95% methylpolysiloxane, 30 m × 0.32 mm (inside diameter) × 0.25 µm (film thickness). Or He is equivalent to a capillary column.

4.3 Microinjectors. 10 µl, 50 µl and 500 µl.

4.4 Separating funnel. 125 ml and 250 ml with Teflon stopper.

4.5 Common instruments and equipment used in general laboratories.

5.1 Sample collection and preservation

A brown glass bottle should be used for sampling. Add 1 ml of sulfuric acid solution (3.7) and 0.5 g of copper sulfate (3.4) per 100 ml of water sample at 4 °C.

Save in the dark. If residual chlorine is present during sampling, add approximately 80 mg of sodium thiosulfate (3.5) to each 100 ml of water and shake well. sample Avoid direct sunlight.

All samples must be extracted within 7 days, and the extract is stored at 4 ° C in the dark and analyzed within 30 days.

5.2 Preparation of samples

5.2.1 Extraction

Take 100 ml of water sample in a 250 ml separatory funnel, add 1 ml of concentrated sulfuric acid (3.6), and extract with 10 ml of n-hexane (3.1).

The water sample was taken twice, and the hexane phase was combined and the aqueous phase was discarded. Then extract the n-hexane phase twice with 0.1 mol/L potassium carbonate solution (3.8) 10 ml, respectively.

The aqueous phase was combined and the n-hexane phase was discarded.

5.2.2 Derivatization

Add 1 ml of acetic anhydride (3.2) to the aqueous phase, shake for 5 min, add 5 ml of n-hexane (3.1), shake for 5 min, and let stand for stratification.

The aqueous phase was discarded and the n-hexane phase was collected. The n-hexane phase was dehydrated with anhydrous sodium sulfate (3.9) and then nitrogen-blown to a volume of 1 ml to be tested.

Note. For high concentration sewage and wastewater samples, appropriate amount of water should be added to the separatory funnel according to the concentration of the sample, and water should be added to 100 ml.

6.1 Chromatographic conditions

6.1.1 Filled Column Gas Chromatography Reference Conditions

Inlet temperature. 220 ° C; detector temperature. 220 ° C; column temperature. 180 ° C; carrier gas flow. 40 ~ 60 ml/min.

6.1.2 Capillary column gas chromatography reference conditions

Inlet temperature. 250 ° C; detector temperature. 300 ° C; column temperature. 60 ° C for 2 min, from 20/min ° C to 220 ° C, Increased from 10/min °C to 250 °C for 3 min; carrier gas flow rate. 1.5 ml/min; tail gas flow rate. 60 ml/min; injection volume. 1.0 µl;

Injection method. no split injection, 0.75 min split after injection, split ratio 40.1.

6.2 Drawing of the working curve

Add 0, 5, 10, 50, 100, 250 to 7 125 ml separatory funnels containing 20 ml of K2CO3 solution (3.8).

500 µl of pentachlorophenol standard use solution (3.12), mix, according to the same procedure of derivatization (5.2.2) to get the concentration of pentachlorophenol is 0, 5, Standard series solutions of 10, 50, 100, 250, 500 ng/ml. 1.0 µl of the standard series solution was injected into the gas phase with a micro-syringe in the spectrometer, the peak area (peak height) of the chromatographic peak corresponding to the solution of different mass concentrations was recorded. Taking the concentration of pentachlorophenol standard series solution as the abscissa, the corresponding peak area (peak height) is the ordinate and the working curve is drawn.

6.3 Chromatogram of standard solution

When using a capillary column and a packed column, respectively, the pentachlorophenyl acetate reference chromatogram is shown in Fig. 1 and Fig. 2.

2 4 6 8 10 12 t/min

1--n-hexane; 2-pentachlorophenyl acetate.

Figure 1 Chromatogram of pentachlorophenyl acetate in a capillary column

2 3 4 5 t/min

1--n-hexane; 2-pentachlorophenyl acetate.

Figure 2 Chromatogram of pentachlorophenyl acetate in packed column

6.4 Determination

1.0 µl of the sample (5.2.2) was injected into the gas chromatograph and measured under the same chromatographic conditions as the working curve. Recording peak Retention time and peak area (peak height).

6.5 Blank test

While the sample is being analyzed, a blank test should be performed. That is, the test water was used instead of the water sample, and the analysis was carried out in the same manner as in the measurement (6.4).

7.1 Calculation of results

The mass concentration (rho) of pentachlorophenol in the sample was calculated according to the formula (1).

rhorho ×= standard (1) where. rho--the concentration of pentachlorophenol in the water sample, µg/L;

rho standard--the concentration of pentachlorophenol calculated from the working curve, µg/L;

1V - the volume of the volume after concentration of the extract, ml;

V -- water sample volume, ml.

7.2 Results representation

When the result is less than 1 µg/L, it is retained to two decimal places; when the result is greater than or equal to 1 µg/L, three significant digits are retained.

8.1 Precision

8.1.1 Capillary column precision

Uniform samples containing 0.05 µg/L, 1.00 µg/L, and 2.50 µg/L of pentachlorophenol were measured in five laboratories.

The relative standard deviations in the experimental room were. 6.0% to 9.7%, 4.4% to 8.0%, and 3.4% to 8.0%;

The relative standard deviations between laboratories were. 7.1%, 6.0%, 1.9%;

The repeatability limits r are. 0.01 µg/L, 0.17 µg/L, 0.38 µg/L;

The reproducibility limits R were. 0.01 µg/L, 0.20 µg/L, and 0.40 µg/L, respectively.

8.1.2 Filled column precision

When the concentration of pentachlorophenol in the sample is less than 2 µg/L, the reproducibility coefficient of variation is less than 9%, and the repeatability coefficient of variation is less than 6%.

8.2 Accuracy

8.2.1 Capillary column accuracy

Five laboratories tested the standard substance containing pentachlorophenol at 102 µg/L. The relative error is -1.9% to 2.2%, and the relative error is finally Value. 0.22% ± 3.94%.

Five laboratories added standard samples of surface water and sewage containing less than 0.01 µg/L and 0.27 µg/L of pentachlorophenol.

The recoveries were 81.8%~96.6% and 89.9%~104%. The final recoveries were 90.1%±10.8% and 97.0%±12.0%, respectively.

8.2.2 Filled column accuracy

When the concentration of pentachlorophenol in the sample is less than 2 µg/L, the recovery rate is greater than 90%, and the coefficient of variation of accuracy is less than 12%.

9.1 Qualitative analysis

A retention time window of t ± 3S should be established prior to sample analysis. t is the average value of the retention time of each concentration level of the reference material at the initial calibration, S is the standard deviation of each standard analysis at the initial calibration. When the sample is analyzed, the sample retention time should be within the retention time window.

9.2 Blank test

Make at least one blank sample and blank spiked sample for each batch of samples. Blank samples are compared with actual samples using the same method, blank the concentration of pentachlorophenol in the sample should be below the detection limit. The recovery rate of the blank sample should be controlled at 80% to 120%.

9.3 The correlation coefficient of the working curve should be greater than or equal to 0.995, otherwise the working curve should be redrawn.

9.4 Intermediate mass concentration test

The intermediate mass concentration test shall be carried out during sample analysis. The relative deviation between the measured value of the intermediate mass concentration and the value of the curve shall be less than or equal to 15%, otherwise a new work curve should be established.

9.5 Matrix addition

At least one matrix spiked sample shall be prepared for each batch of samples. The matrix spiked sample and the actual sample shall be analyzed and determined by the same method.

The recovery rate should be controlled at 70% to 130%.

Appendix A

(informative appendix) Filling method of packed column Weigh 5% of the weight of the coated OV-17 (polymethylsiloxane containing phenyl) on a thousandth of a balance and take up the load.

2% by weight of QF-1 was placed in a small beaker and dissolved in methylene chloride in an amount sufficient to submerge the support. Transfer the solution to 250 ml in the round bottom flask, a weighing carrier to be coated was added, and the condenser was attached, and the mixture was heated under reflux for 2 hours. Then, place the flask in the warm on the water bath, depressurize with a water pump to slowly evaporate the solvent. Finally, the support is placed in a petri dish and baked with an infrared lamp for later use.

The end of the column (connected to the detector end) is plugged with quartz wool, connected to a vacuum pump, and the other end of the column is connected to a funnel through a hose.

After the vacuum pump, the stationary phase is slowly loaded into the column through the funnel, and the column is tapped while packing to make the filling uniform. After filling, use quartz Cotton is plugged into the other end of the column.

The filled column is connected to the inlet of the instrument, and the detector is not connected at one end. The carrier gas is supplied at a flow rate of 20-30 ml/min. The column oven is maintained.

Continuous aging for 48 h at 240 °C. Check before use, straighten to the baseline.